When a motor is operating, coils, cores and other components may have energy loss, this part of loss is eventually dissipated in the form of heat energy. Radial ventilation cooling is one of commonly used cooling manners for the motor. This cooling manner can increase the heat dissipation area and improve the power density of the generator, thus it has been widely used.
As shown in FIG. 1, the core of the motor is divided into multiple core sections 11, a ventilation channel steel 12 is provided between adjacent core sections 11 in a radial direction of the motor. The ventilation channel steel 12 has a supporting effect to the core sections 11, and also divides the space between adjacent core sections 11 into a ventilation channel 13. The motor has a recirculation ventilation path in which a cold air enters an air gap 14 from an end of a winding (not shown) and passes through the ventilation channel 13 (for example, branch ventilation channels 1 to 8 in the Figure), and reaches a cavity between two core brackets 15, and finally the hot air in the cavity is drawn through a pipeline to a heat exchanger outside the motor and converted into a cold air by the heat exchanger, and then the cold air enters the inside of the motor. As shown in FIG. 2, the ventilation channel steel 12 in the conventional radial ventilation cooling structure for the motor is a bar-shaped ventilation channel steel having a rectangular cross section, and the height of the ventilation channel 13 in an axial direction of the motor, that is the height h of the ventilation channel steel 12 in the axial direction of the motor (as shown in FIGS. 1 and 2), is equal to the distance between adjacent core sections 11 in the axial direction of the motor.
In the process of implementing the above ventilation cooling, the inventors have found that there are at least the following issues in the conventional technology. After the airflow enters the air gap, the velocity of the airflow is continuously reduced due to the bypassing effect, a local drag and a frictional drag of the ventilation channels and the like, thus the static pressure is increasingly greater and the dynamic pressure is increasingly smaller from an inlet of the air gap to a middle position of the air gap. However, since the multiple ventilation channel steels has the same structure and the multiple core sections has the same structure, the multiple ventilation channels have the same impedance, thus the quantity of airflow flowing through the multiple ventilation channels are increasingly larger. The heat generated by the internal heat source (coils, cores, and etc.) of the motor is distributed uniformly in the axial direction of the motor, while the airflow flowing through the multiple ventilation channels is distribute non-uniformly, thus the distribution of the temperature of the coils and the multiple core sections in the axial direction of the motor is not uniform, and the temperature from the inlet of the air gap to the middle position of the air gap is increasingly lower. The distribution of the temperature of the coils and the multiple core sections in the axial direction of the motor is not uniform, and the maximum temperature value is great, which is apt to cause a too high local temperature rising phenomenon, resulting in a shutdown of the motor, and is also apt to cause the core bracket to be thermally deformed, and therefore affecting the normal operation of the motor.